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<br /> A S S O C I A T E S I N C
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<br /> used to develop the groundwater elevation contour map (Figure 5) Assuming that horizontal
<br /> isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed
<br /> towards the northwest The average hydraulic gradient on December 19, 2001 was calculated to
<br /> be 0 009 ft/ft or approximately 48 ft/mile
<br />' The average groundwater elevation of the on-site shallow wells MW1 through MW3 on
<br /> December 17, 2001 was approximately —35 76 feet above sea level This is 0 06 feet less than
<br /> the groundwater elevation in the deep well, MW8, which means that the vertical gradient at the
<br /> site was upward A summary of groundwater monitoring data is presented in Table 3
<br />' 4.0 DISTRIBUTION OF PETROLEUM HYDROCARBONS
<br /> 4.1 Petroleum Hydrocarbons in Soil
<br />' Soil samples collected from borings MW9, MW10, S131, SB2, SB3, and SB4 contained no
<br /> detectable concentrations of TPHg, BTEX, MTBE, TAME, ETBE, DIPS, TBA, 1,2-DCA, or
<br /> t EDB Soil samples collected from borings VW 1 and V W2 contained trace concentrations of
<br /> TPHg and BTEX constituents, but contained no detectable concentrations of MTBE, TAME,
<br /> ETBE, DIPE, TBA, 1,2-DCA, or EDB Soil samples collected from borings AS 1, PZIa, PZ1b,
<br /> } and V W3 contained detectable concentrations of TPHg and BTEX, but contained no detectable
<br /> concentrations of MTBE, TAME, ETBE, DIPE, TBA, 1,2-DCA, or EDB Analytical results of
<br /> soil samples are summarized in Table 1 Laboratory data sheets and chain-of-custody
<br /> documentation for soil samples are presented in Appendix C
<br /> 4.2 Petroleum Hydrocarbons in Groundwater
<br /> The groundwater samples collected in August 2001 from borings SB 1 through S133 contained no
<br />' detectable concentrations of TPHg, BTEX, MTBE, TAME, ETBE, DIPE, TBA, 1,2-DCA, or
<br /> EDB The groundwater sample collected from boring S134 contained detectable concentrations
<br /> of TPHg and BTEX, but contained no detectable concentrations of MTBE, ETBE, DIPE, TAME,
<br />' TBA, 1,2-DCA, or EDB
<br /> The groundwater samples collected in September 2001 from groundwater monitoring wells
<br /> MWS, MW9, and MW 10 contained no detectable concentrations of TPHg, BTEX, MTBE,
<br /> TAME, ETBE, DIPE, TBA, 1,2-DCA, or EDB The groundwater samples collected from
<br /> groundwater monitoring wells MW4, MW7, and MW8 and drinking water well DW contained
<br />' detectable concentrations of TPHg and BTEX, but contained no detectable concentrations of
<br /> MTBE, TAME, ETBE, DIPE, TBA, 1,2-DCA, or EDB The groundwater samples collected
<br /> from groundwater monitoring wells MWI, MW2, MW3, MW6, air sparge well ASI, and
<br />' piezometers AS 1(s), AS 1(d), PZ 1 a(s), PZ 1 a(d), and PZ 1 b(d) contained the highest
<br /> concentrations of TPHg and BTEX, but contained no detectable concentrations of MTBE,
<br /> TAME, ETBE, DIPE, TBA, 1,2-DCA, or EDB Isoconcentration maps depicting the benzene
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